According to scientific research, one psychologist told me, human fears are at least partly erasable. All it takes is a single pill.

The latest evidence of that phenomenon comes from a study published in December 2015 by researchers at the University of Amsterdam.

For the study, the researchers recruited 45 women who reported being afraid of spiders. All the women were asked to open a jar with a baby tarantula inside, touch the spider, let it walk on their bare hands, and report how frightened they felt. They were allowed to stop the procedure at any point — and none of the participants ended up getting to the point where they touched the spider.

Next, some of the women were given a pill containing the drug propranolol, while the rest were given a placebo. Propranolol is a beta-blocker, which means it blocks the hormone adrenaline. (None of the women knew what pill they were consuming.)

Four days later, all the participants returned to the lab. Some were asked to touch the tarantula again and report how frightened they felt; others weren't.

Sure enough, all the women who'd taken propranolol were able to touch the tarantula, and reported being less afraid. On the other hand, none of the women who'd taken the placebo were able to touch the spider as instructed. And the women who'd taken the propranolol without touching the spider reported being just as fearful as they were before.

The really scary part? Even one year later, these effects persisted.

In other words, propranolol plus being re-exposed to the tarantula seemed to reduce the women's fear of spiders.

That's likely because propranolol blocks a chemical in the brain that facilitates learning, meaning it disrupts the process of "memory reconsolidation," or the way a memory is stored after it's retrieved.

This study builds on previous research on rats, which found that there's a brief window of time during memory reconsolidation when memories can be altered.

You might still think you're scared after taking propranolol — but you'll be better able to face your fears.Flickr / Laura Hadden
More recently, propranolol has also been used to reduce stage fright and improve performance by blocking the effects of the hormone adrenaline. (Drug companies aren't allowed to market it for anxiety and stage fright though, because the FDA hasn't approved it for those usages.)

Merel Kindt, a coauthor on the tarantula study, said the use of propranolol to treat fear and anxiety differs from traditional cognitive behavioral therapy (CBT) in one key way. In CBT, people start to change their thoughts, which in turn can cause behavior changes.

When people consume propranolol, however, their behavior changes first and then their thoughts change. Case in point: The women who took propranolol still said they were nervous when they were asked to handle the tarantula a second time, but they were nonetheless able to touch it and reported being less afraid during the experience.

As Kindt said: "It is almost as if their autobiographical memory still has to adapt to the fact that the physical fear response has vanished."

Kindt said it's still unclear whether propranolol will eventually overtake CBT and similar therapies. "When it does succeed, however, the treatment is more effective and more rigorous than traditional therapy. It is also less invasive and the use of propranolol only a one-off, as opposed to established anti-anxiety meds that need to be taken regularly and pose risks in terms of addiction and withdrawal."